1. Field of the Invention
The present invention relates to a write-once optical disc, and more particularly, to an apparatus and method for allocating a spare area on a write-once optical disc such as a write-once blu-ray disc.
2. Discussion of the Background Art
A new type of high density optical disc such as a Blu-ray Disc Rewritable (BD-RE) is being developed. A benefit of the BD-RE is that it has a rewritable capability where the quality video and audio data can be written, erased and rewritten thereon repeatedly.
FIG. 1 is a block diagram of a general optical disc device for writing/reproducing data to/from an optical disc such as a BD-RE. As shown in FIG. 1, the optical disc device includes an optical pickup 11 for recording/reproducing a signal to/from a BD-RE 10, a video disc recorder (VDR) system 12 for processing a signal from the optical pickup 11 as a reproduced signal, or demodulating and processing an external data stream into a writable signal suitable for writing onto the BD-RE 10, and an encoder 13 for encoding an external analog signal and providing the encoded signal to the VDR system 12.
FIG. 2 shows a structure of a general BD-RE. Referring to FIG. 2, an LIA (lead-in area), a data area and an LOA (lead-out area) are allocated on the BD-RE. An ISA (inner spare area) and an OSA (outer spare area) are allocated separately to a front and a rear end of the data area. A user data area having an LSN (Logical Sector Number) is allocated between the ISA and the OSA of the data area.
Referring to FIGS. 1 and 2, the VDR system 12 writes input data from an external source in a cluster unit corresponding ECC block having a predetermined recording capacity after encoding and converting the input data into a recording signal. The VDR system 12 also detects a defective area within the data area when recording the data.
When a defective area is detected, the VDR system 12 performs a replacement writing operation to write the cluster data from the defective area onto the ISA instead. After the data writing is finished, location information of the defective area and management information for reproducing the cluster data written on the spare area (replacement area) are written as a defect list onto the LIA.
FIGS. 3A and 3B illustrate a general structure of a BD-RE single layer and a BD-RE dual layer, respectively. As shown, a BD-RE may have a single recording layer (FIG. 3A) or two recording layers (FIG. 3B).
Referring to FIG. 3A, the recording capacity of the inner spare area ISA being allocated to the BD-RE single layer is 2048 clusters, and the recording capacity of the outer spare area OSA is N×256 (0=<N<=64) clusters with a maximum of 16384 clusters. The recording capacity of the data area of the BD-RE single layer is 355603 clusters. The recording capacity of the user data area of the BD-RE single layer is determined to be a difference between the recording capacity of the data area and the recording capacity of the spare areas. For example, when the recording capacity of the outer spare area is 16384 clusters (N=64), then the recording capacity of the user data area is 337171 clusters. As a result, the size of the inner and outer spare areas (18432=2048+16384) corresponds to 5.5% of the size of the user data area of the BD-RE single layer.
Referring to FIG. 3B, in the BD-RE dual layer, the recording capacity of the inner spare area (ISA0) of a first layer (Layer 0) is 2048 clusters. The recording capacity of the outer spare area (OSA0) of the first layer is N×256 clusters (0=<N<=32) with the 8192 maximum clusters (N=32). On the other hand, the recording capacity of the inner spare area (ISA1) of a second layer (Layer 1) is L×256 clusters (0=<L<=64) with the 16384 maximum clusters (L=64). The recording capacity of the outer spare area (OSA1) of the second layer is N×256 clusters (0=<N<=32) with the 8192 maximum clusters (N=32). As a result, the total recording capacity of the spare areas of the first and second layers is calculated to be 5.1% of the total recording capacity of the user data areas of the first and second layers.
A Blu-ray Disc Write-Once (BD-WO) is another type of high density optical disc that is being developed where a high quality of data can be recorded and reproduced to and from the disc. As the name may suggest, data can be written only once on the BD-WO and is not rewritable on the BD-WO. But the BD-WO can be read repeatedly. As a result, the BD-WO is useful where the rewritability of data on a recording medium is not desired.
Recently, standardizing the size of the BD-WO is being considered. But allocating the spare areas of the BD-WO as in the BD-RE would cause a problem of wasting precious recording space due to the characteristics of the BD-WO. For instance, in the BD-RE the recording capacity of the spare areas should be allocated large enough since the BD-RE re-records data repeatedly and as a result many defective areas can surface. In contrast, BD-WO is able to write once and thus relatively less defective areas may be present. Therefore, it is not necessary and is wasteful to allocate the same amount of spare area of the BD-RE onto the BD-WO.